Efficiency optimized air flow apparatus and method of operation

ABSTRACT

A method for controlling the motor of an air handling system to provide a desired output of flowing air therefrom while minimizing the power used by the motor, including operationally connecting a switched reluctance electric motor to a blower, operationally connecting an electronic controller to the switched reluctance electric motor, operationally connecting at least one sensor to the electronic controller, measuring at least one environmental parameter with the at least one sensor, inputting the desired air flow into the electronic controller, calculating the minimum motor speed necessary to provide the desired air flow, and sending a control signal from the electronic controller to the motor to control the motor to the minimum motor speed necessary to provide the desired air flow.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of co-pending U.S. patentapplication Ser. No. 12/704,949, filed on Feb. 12, 2010.

TECHNICAL FIELD

The present novel technology relates generally to air flow control inair handling systems, and, more particularly, to a method and apparatusfor optimizing the efficiency of the air handling system whilemaintaining constant air flow by a blower operationally connected to thesystem.

BACKGROUND

Air handling systems, whether residential, commercial, or municipal,typically use a blower to urge air of a predetermined temperaturethrough a duct system to control and maintain the temperature of anenclosure. The blower typically includes a fan operationally connectedto a motor. The motor is typically electric. The air handling system istypically required to provide air flow under a variety of conditions,including variable enclosure volume, the temperature of the enclosure,the temperature of the air delivered, the duct geometry, and the like.

Typically, an air handling system is required to provide air at aconstant flow rate. A constant flow rate is generally achieved bycontrolling the speed of the driver motor in response to detectedchanges in the air flow rate and/or related variables. A number ofcontrol paradigms have been developed to control air flow rate bycontrolling motor speed, the specifics of each tailored to thecharacteristics of the hardware, desired output, and buildingenvironment of the particular air handling system in question.

Typically, the electric motor driving the blower fan is a synchronousand operating at fixed increments of speed, such as 600 RPM, 900 RPM,1800 RPM, 3600 RPM and the like. In order to effectively operatesynchronous motors at speeds other than their incremental options, themotors must be connected to the blower fan via an adaptor, such as aV-belt or the like, whereby the motor speed may be relatively smoothlystepped up or down as desired. The drawback of this approach is thatsuch adaptor systems are somewhat inefficient, costing the system extraenergy. Further, such systems contribute to increased noise output andthe requirement of sound insulation, more powerful electronic controllercapability, and additional control and feedback modules.

Further, the standard electric motors and blowers of existing airhandling systems are designed to more or less efficiently operate arounda narrow plateau of operating speeds and are typically designed to mostefficiently operate around the speeds correlating to the standard andmost common air flow demand. When demand spikes, it becomes veryinefficient and even stressful to the system to ramp up to meet thesudden increase in demand for air flow, if the motor can evenaccommodate the demand at all. Thus, it is often necessary to haveseveral independent and redundant air handling systems in place tohandle acute, unusually heavy demands. For example, water treatmentplants have two, and sometimes three, separate air handling systems inplace to handle increased water demand due to heavy rainstorms ormorning and evening heavy load times. The drawback of this configurationis that energizing the redundant blower unit often supplies more airflow than is required for the process, resulting in unneeded powerconsumption. Alternatively, an induction motor and VFD can be used, toadjust the blower airflow and meet process demands However, inductionmotors operate at less than their optimum efficiency when run at lessthan full motor load. Also, these motors have a relatively steepefficiency drop as motor speed moves away from the optimal. Finally,there is an added cost to supplying and maintaining several independentblower units for one job.

Thus, there is a need for an air handling system having a motor capableof directly providing variable output speeds and a method and apparatusfor controlling the same to optimize the efficiency of the air handlingsystem while providing a constant air flow output. The present noveltechnology addresses these needs.

SUMMARY

The present novel technology relates to an improved air handling controlsystem. It is an object of the present novel technology to overcome thedrawbacks associated with the conventional air handling delivery andcontrol methods. The present novel technology relates generally to animproved air handling control system.

One object of the present novel technology is to provide an improvedmethod of air handling delivery and control. Further objects, features,and advantages will become apparent from a consideration of thefollowing description.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the nature and objects of the presentnovel technology, reference should be made to the following drawings, inwhich:

FIG. 1 is a block diagram illustrating a first embodiment of the presentnovel technology, an apparatus for controlling the operation of a blowerto yield increased efficiency.

FIG. 2 is a block diagram illustrating the embodiment of FIG. 1 used toprovide flowing air in a waste water treatment application.

FIG. 3 is a graphic illustration of the relationship between blowerspeed and system efficiency.

FIG. 4 is a block diagram illustrating an example method of regulating ablower assembly to minimize power usage while achieving a desiredeffect.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of thenovel technology, reference will now be made to the embodimentsillustrated in the drawings and specific language will be used todescribe the same. It will nevertheless be understood that no limitationof the scope of the novel technology is thereby intended, suchalterations and further modifications in the illustrated device, andsuch further applications of the principles of the novel technology asillustrated therein being contemplated as would normally occur to oneskilled in the art to which the novel technology relates.

A first embodiment of the present novel technology is illustrated inFIG. 1, and relates to an air handling system 10 that includes anelectric motor 20 operationally connected to a blower 25 and connectedin electric communication to an electronic controller or microprocessor30. In some embodiments, the microprocessor 30 is connected to the motor20 through switch 33, which is typically connected to a power source(not shown). The electric motor 20 is more typically a switchedreluctance motor. One or more sensors 35 are arrayed throughout thesystem 10 and also electrically connected to the microprocessor 30. Thesystem 10 is typically a ‘middle pressure’ system, operating to providean output pressure of between about 4 and about 20 psig.

The sensor array 35 typically may include an air flow sensor 40positioned to measure the flow rate of the air as urged by the blower25. Also, the sensors 35 may include a barometric pressure sensor 45and/or ambient air relative humidity sensor 50 and/or an ambient airtemperature sensor 55 and/or a dissolved oxygen sensor 60 and/or thelike, each positioned to measure respective properties of the fluid intowhich the system 10 outputs its flowing air (i.e., ambient air in abuilding or enclosure, water in a water treatment reservoir, or thelike).

The sensor array 35 typically includes a blower speed sensor 70 and/or ablower discharge temperature sensor 75 and/or a blower dischargepressure sensor 80 and/or a blower inlet pressure sensor 85 the like,each positioned to measure respective properties associated with theblower. Likewise, the sensor array 35 typically includes a motor voltagesensor 90 and/or a motor amperage sensor 95 and/or the like, eachpositioned to measure properties associated with the electric motor 20.

While the system 10 may include an air flow sensor 40 positionedupstream or downstream of the blower 25 for providing a control feedbacksignal to the microprocessor 30, air flow sensors typically have anerror margin of +/−5% or greater. A more precise method of determiningair flow is to calculate from the blower motor speed and air parametersthat are measureable with greater precision. For example, in oneparticular embodiment system 10, the motor 20 is a switched reluctancedrive motor provided by Switched Reluctance Drives, Ltd., East ParkHouse, Otley Road, Harrogate, UK, HG3 1PR, and the following inputs arereceived by the microprocessor 30 from the sensor array 35:

Relative Humidity (Φ) % Atmospheric Pressure (P_(atm)) PSIA Pressuredrop across inlet filter (P_(in)) Inches Water Column Inlet Pressure atblower flange (P₁) PSIG Inlet Temperature at air inlet (T₁) DegreesRankine Discharge pressure at blower flange (P₂) PSIG Dischargetemperature at blower flange (T₂) Degrees Rankine Motor/Blower Speed (ν)RPM and Standard Pressure (P_(std)) 14.7 PSIA Standard Temperature(T_(std)) 528 Degrees Rankine Standard Relative Humidity (Φ_(std)) 36%are given as predetermined values. From these data, ICFM (Inlet CubicFeet per Minute) may be calculated for the system 10, typically based onproprietary equations provided by the blower manufacturer. Theseproprietary equations are programmed into the microprocessor 30 and,using these, ICFM is determined. From the ICFM value a conversion toSCFM (Standard Cubic Feet per Minute) is made; the ICFM is essentially avolumetric value while the SCFM is an air mass (or oxygen mass) value.The equation used for the conversion is as follows:

${S\; C\; F\; M} = {I\; C\; F\; M*T_{sid}*\left( \frac{P_{atm} - {P_{sat}*\varphi}}{T_{1}*P_{std}} \right)}$

where P_(sat) is determined from published tables for air based on T₁.

In general, for rotary lobe positive displacement blowers the ICFM canbe determined using the variables listed above along with a value forthe Cubic Feet per Revolution (CFR) and the Slip RPM for a particularblower. Slip RPM is the speed at which 1 PSI of discharge pressure isdeveloped with the discharge. ICFM may thus be expressed as:

${I\; C\; F\; M} = {C\; F\; R*\left\lbrack {{{Blower}\mspace{14mu} {Speed}} - {{Slip}\mspace{14mu} R\; P\; M*\sqrt{\left( {P_{2} - P_{1}} \right)*\frac{T_{1}}{T_{std}}*\frac{G_{s}}{G_{a}}}}} \right\rbrack}$

Where G_(s) and G_(a) are standard specific gravity of air and theactual specific gravity of the process gas, respectively. G_(s) is givenas 1.0. G_(a) is determined by the following relation:

$G_{a} = {{\left( \frac{P_{1} - {P_{sat}*\varphi}}{P_{1}} \right)*{MW}_{dry}} + {\left( \frac{P_{sat}*\varphi}{P_{1}} \right)*{MW}_{wv}}}$

where the MW terms are the molecular weights of the components of theprocess gas, which consists of dry air and water vapor. Their values areas follows:

MW_(dry)=28.964 lbm/lb mol

MW_(wv)=18.02 lbm/lb mol

An alternate method for calculating SCFM from ICFM follows as:

${S\; C\; F\; M} = {I\; C\; F\; M*\left( \frac{P_{1}}{P_{std}} \right)\left( \frac{T_{std}}{T_{1}} \right)\left( \frac{1 + \omega_{std}}{1 + \omega_{1}} \right)\left( \frac{{MW}_{1}}{{MW}_{std}} \right)}$

where ω_(std) is standard humidity ratio and may be expressed as:

$\omega_{std} = {\left( \frac{\varphi_{std}*P_{v_{1}{sat}_{std}}}{P_{std} - {\varphi_{std}*P_{v_{1}{sat}_{std}}}} \right)\left( \frac{{MW}_{wv}}{{MW}_{dry}} \right)}$

and ω₁ is inlet humidity ratio and may be expressed as:

$\omega_{1} = {\left( \frac{\varphi_{1}*P_{v_{1}{sat}_{1}}}{P_{1} - {\varphi_{1}*P_{v_{1}{sat}_{1}}}} \right)\left( \frac{{MW}_{wv}}{{MW}_{dry}} \right)}$

with MW₁ equivalent to G_(a) above.

In operation, the motor 20 is typically run to provide a constant speed,constant air flow, or varied speed based on a predetermined parameter,such as dissolved oxygen demand. The electronic controller 30 monitorsthe input from the sensor array 35, calculates the optimum motor speedto provide the required output at a minimum energy use, andautomatically controls the motor speed to maximize system efficiency.The sensor array 35 includes sensors 40, 45, 50, 55, 60, 70, 75, 80, 85,90, 95 for measuring one or more parameters from the set including airflow, dissolved oxygen, blower discharge pressure, blower dischargetemperature, blower inlet pressure, ambient air relative humidity,ambient air temperature, barometric pressure, blower speed, motorvoltage, and motor amperage. The electronic controller 30 uses data fromthe sensor array 35 to calculate the optimal motor speed for achievingdesired motor/controller efficiency, such as, for example of about 90%when system is at about 66% load, or efficiency of about 85% when systemis at about 33% load, or efficiency of about 55% when system is at about66% load, or efficiency of about 50% when system is at about 33% load,or the like. Further, the electronic controller 30 uses data from thesensor array 35 to calculate the optimal motor speed for providing adesired air flow with minimized power consumption, such that themotor/controller efficiency is, for example, at least 90% (or at leastabout 80%, or at least about 55%, or at least about 50% or the like)when the system 10 is at full load and motor speed is within a range offrom about 500 RPM to about 3500 RPM or the like.

Water Treatment Applications

Dissolved oxygen in water treatment is required for the aerobicmicroorganisms that are used to convert unwanted organic wastes to inertinorganic byproducts. In order for these microorganisms to thrive, thedissolved oxygen content of the water is desired to be maintained abovea certain threshold level, typically around 2 mg per liter of water. Theactual value in any specific case is predetermined by the treatmentfacility and is typically measured and verified manually by a laboratorytechnician. Typically, the technician will go to an aeration basin,remove a water sample, determine the dissolved oxygen content and thendetermine whether more or less air is being supplied to the tank than isneeded to maintain the dissolved oxygen content at an acceptable level.

For water treatment, the system 10 is typically utilized to provide airflow for scouring and backwashing water filters. Scouring andbackwashing are typically constant flow applications, wherein pressuremay sharply increase or spike upon startup of the air directing ductworkleading from the blower 20 into the water reservoir, until water clearsthe discharge line. The system 10 may also be connected as part of apneumatic conveying system for dry chemicals. This configuration wouldlikewise typically be a constant flow application.

For wastewater treatment applications, the system 10 may be connected toprovide air for pre-aeration, secondary aeration, more scour andbackwash, and mixing. The system 10 is suited for use in applicationsrequiring varying flow and aeration, the blower(s) 25 provides airthrough a duct or conduit 110 to the bottom of a tank or basin 120,typically through one or more diffusers 125. The diffusers 125 portionthe air into small diameter bubbles 130 in order to maximize the surfacearea of the air volume so introduced into the waste water 135. Diffusionof oxygen into the mixture occurs as the bubbles 130 rise through thewaste water 135. The oxygen is used by bacteria in a biological processto break down solid organic wastes and contaminants. Oxygen demand bythe process fluctuates regularly due to changes in the amount ofinfluent waste, composition of the influent, and environmentalconditions. If oxygen demand drops, less airflow can be provided to thesystem and operating cost is reduced. Typically the feedback is providedby a dissolved oxygen probe or sensor 60. These are typically constantpressure, variable volume applications.

Typically, mixing applications require a set airflow for a given volumeof waste water 135. Air is provided again through diffusers 125,however, these diffusers 125 are configured to produce larger bubbles130 in order to induce greater fluid displacement and, thus, morethorough mixing. Some oxygen transfer is still required, as there is abiological process occurring, but the main concern is maintaining ahomogenous fluid mixture. Effective water volume does fluctuate with theamount of influent, therefore the application is variable volume andvariable pressure.

Treatment water 135 having a dissolved oxygen content above the valuerequired for the waste-reducing microorganisms to proliferate providesno benefit, and represents an added and unnecessary expense. The system10 measures the dissolved oxygen content with one or more oxygen sensors60 positioned in the water reservoir or basin 120 to provide real-timefeedback to the microprocessor 30, as well as to system operators, toindicate what adjustments, if any, should be made to provide sufficient,but not excessive, airflow to the water reservoir 120 to maintain thedissolved oxygen concentration at the desired, predetermined level. Thesystem 10 typically receives a signal from the sensor 60 andautomatically adjusts the speed of the blower 25 to provide increased ordecreased air flow into the water reservoir 120 as indicated by thesensor 60 and determined by the microprocessor 30 to yield sufficient,but not excessive, dissolved oxygen for the waste reducingmicroorganisms to live in the water reservoir 120. The signal from thesensor 60 is typically a low current signal, more typically in the 4 mAto 20 mA range. This blower 25 may be energized by the motor 20 to runfaster or slower to provide increased or decreased air flow dependingupon feedback from the dissolved oxygen probe 60 and/or other sensors inthe sensor array 35 while maintaining substantially optimum efficiency,without the need of one or more redundant backup blower systems on line.The system efficiency curve plotted as a function of blower speed forvarious loads is given as FIG. 4.

FIG. 3 is a block diagram 300 illustrating an example method ofregulating a blower assembly 25 to minimize power usage while achievinga desired effect. Desired operating characteristics are received (302)by a microprocessor 30. For example, a specific air flow rate or airpressure may be desired. In some implementations, the desiredcharacteristic may be calculated based upon sensor data obtained fromthe sensor array 35. For example, a desired dissolved oxygen contentnecessary for a desired microbial activity can be calculated based uponthe temperature of an effluent that is being aerated.

The microprocessor 30 receives sensor data (304) from the sensor array35. In some implementations, the sensor array 35 includes sensors 40,45, 50, 55, 60, 70, 75, 80, 85, 90, 95 for measuring one or moreparameters from the set including air flow, dissolved oxygen, blowerdischarge pressure, blower discharge temperature, blower inlet pressure,ambient air relative humidity, ambient air temperature, barometricpressure, blower speed, motor voltage, and motor amperage. Themicroprocessor uses the sensor data to calculate the required minimumblower speed (306) necessary to achieve the desired operatingcharacteristic. The microprocessor 30 regulates the blower assembly 25to achieve the required minimum blower speed (308).

Other Applications

In a dilute phase pneumatic conveying application, the air handlingsystem 10 is engaged to maintain a minimum airflow velocity for thehighest density particle stream. Where particles of lesser density orvarying physical characteristics are introduced into the stream, theadditional airflow velocity is not required in order to maintain theminimum flow velocity. Energy can be conserved by measuring particlevelocity with the sensor array 35, such as via radar or the like, andcommunicating the particle velocity measurement signal to themicroprocessor 30, which then automatically calculates the minimumblower 20 speed necessary to yield the minimum airflow velocity requiredto maintain the required conveyance speeds. This would be defined as avariable flow and pressure application.

While the novel technology has been illustrated and described in detailin the drawings and foregoing description, the same is to be consideredas illustrative and not restrictive in character. It is understood thatthe embodiments have been shown and described in the foregoingspecification in satisfaction of the best mode and enablementrequirements. It is understood that one of ordinary skill in the artcould readily make a nigh-infinite number of insubstantial changes andmodifications to the above-described embodiments and that it would beimpractical to attempt to describe all such embodiment variations in thepresent specification. Accordingly, it is understood that all changesand modifications that come within the spirit of the novel technologyare desired to be protected.

We claim:
 1. An efficiency-optimized air handling system, comprising: ablower; a switched reluctance electric motor operationally connected tothe blower; an electronic controller operationally connected to theswitched reluctance electric motor; and a sensor array operationallyconnected to the electronic controller; wherein the sensor arrayincludes sensors for measuring one or more parameters from the setincluding air flow, dissolved oxygen, blower discharge pressure, blowerdischarge temperature, blower inlet pressure, ambient air relativehumidity, ambient air temperature, barometric pressure, blower speed,motor voltage, and motor amperage; wherein the electronic controlleruses data from the sensor array to calculate the optimal motor speed forachieving motor/controller efficiency of over 90% when the system is atfull load.
 2. The air handling system of claim 1, wherein the electroniccontroller uses data from the sensor array to calculate the optimalmotor speed for achieving motor/controller efficiency of about 90% whensystem is at about 66% load.
 3. The air handling system of claim 1,wherein the electronic controller uses data from the sensor array tocalculate the optimal motor speed for achieving motor/controllerefficiency of about 85% when system is at about 33% load.
 4. The airhandling system of claim 1, wherein the electronic controller uses datafrom the sensor array to calculate the optimal motor speed for providinga desired air flow with minimized power consumption, such that themotor/controller efficiency is at least 90% when the system is at fullload and motor speed is within a range of from about 500 RPM to about3500 RPM.
 5. An efficiency-optimized air handling system, comprising: ablower; a switched reluctance electric motor operationally connected tothe blower; an electronic controller operationally connected to theswitched reluctance electric motor; and a sensor array operationallyconnected to the electronic controller; wherein the sensor arrayincludes sensors for measuring one or more parameters from the setincluding air flow, dissolved oxygen, blower discharge pressure, blowerdischarge temperature, blower inlet pressure, ambient air relativehumidity, ambient air temperature, barometric pressure, blower speed,motor voltage, and motor amperage; wherein the electronic controlleruses data from the sensor array to calculate the optimal motor speed forachieving a blower efficiency of over 60% when the system is at fullload.
 6. The air handling system of claim 5, wherein the electroniccontroller uses data from the sensor array to calculate the optimalmotor speed for providing a desired air flow with minimized powerconsumption, such that the blower efficiency is at least about 80% whenthe system is at full load and the motor speed is within a range of fromabout 500 RPM to about 3500 RPM.
 7. An efficiency-optimized air handlingsystem, comprising: a blower; a switched reluctance electric motoroperationally connected to the blower; an electronic controlleroperationally connected to the switched reluctance electric motor; and asensor array operationally connected to the electronic controller;wherein the sensor array includes sensors for measuring one or moreparameters from the set including air flow, dissolved oxygen, blowerdischarge pressure, blower discharge temperature, blower inlet pressure,ambient air relative humidity, ambient air temperature, barometricpressure, blower speed, motor voltage, and motor amperage; wherein theelectronic controller uses data from the sensor array to calculate theoptimal motor speed for achieving an overall system efficiency of over50% when the system is at full load.
 8. The air handling system of claim7, wherein the electronic controller uses data from the sensor array tocalculate the optimal motor speed for achieving an overall systemefficiency of over 55% when the system is at 66% load.
 9. The airhandling system of claim 7, wherein the electronic controller uses datafrom the sensor array to calculate the optimal motor speed for achievingan overall system efficiency of over 50% when the system is at 33% load.10. The air handling system of claim 7, wherein the electroniccontroller uses data from the sensor array to calculate the optimalmotor speed for providing a desired air flow with minimized powerconsumption, such that the overall system efficiency is at least about55% when the system is at full load and the motor speed is within arange of from about 500 RPM to about 3500 RPM.
 11. An efficiency processcontrol system for a constant air flow air handling system comprising: ablower assembly comprising electric variable speed motor operationallyconnected to a blower; a microprocessor in electric communication withthe blower assembly; and a sensor array in electric communication withthe microprocessor and having an air flow sensor, a blower speed sensor,an oxygen sensor, and a motor amperage sensor; wherein the air flowsensor is positioned to measure an air flow rate of air urged by theblower assembly; and wherein the microprocessor receives sensor datafrom the sensor array and calculates the minimum blower speed requiredto achieve a desired air flow based upon the sensor data andelectronically communicating the minimum blower speed to the blowerassembly.
 12. A method for efficiently running a blower assemblycomprising: receiving, by a microprocessor, sensor data, the sensor dataobtained from a sensor array comprising an air flow sensor, a blowerspeed sensor, an oxygen sensor, and a motor amperage sensor;calculating, by the microprocessor, a minimum blower speed required toachieve a desired air flow based upon the sensor data; and regulating aspeed of a blower assembly, by the microprocessor, such that the blowerassembly is operated at the minimum speed required to achieve thedesired air flow.